The invention concerns a process for controlling and regulating a clutch in a stepped load-switchable automatic transmission for a motor vehicle, where an electronic control apparatus with two control circuits determines the behavior of the clutch. The invention further relates to an apparatus for carrying out the process for controlling and regulating a clutch in a motor vehicle drive.
A clutch is to be understood is to be understood in the sense of the invention as a startup clutch. Under these fall clutches arranged between an internal combustion engine and an automatic transmission, transformer bypass clutches, as well as clutches and brakes arranged in the automatic transmission, which can be used for starting up as well as shifting clutches.
The invention especially concerns wet-running startup clutches, which can be integrated into automatic transmissions. Nevertheless, usually these startup transmissions are arranged as a assembly groups on the transmission input, for example, also as a startup element in an automated stepped transmission. Especially in continuously variable transmissions, the wet startup clutch is also arranged as an assembly group on the transmission output.
Clutches and brakes are usually electro-hydraulically activated in the automatic transmission or in the automated stepped transmission independently of the use of the switch elements such as gear change clutches, startup clutches, or transformer bypass clutches. For this purpose, usually vehicle-specific, transmission-specific and operating condition-specific magnitudes, such as, for example, axle and gear ratios, engine torque, engine speed, gas pedal setting or the like, are processed in an electronic transmission control device and appropriate clutch-relevant output signals, for example, for pressure control or pressure regulation or during a gear shift or for rotational speed regulation during a drifting operation, transmitted to a hydraulic control apparatus, and there converted by means of actuators and hydraulic valves into hydraulic control pressures for the corresponding clutch.
A process for controlling a startup clutch is, among other things, known from DE 44 09 122 A1. The startup control unit herein consists of two phases; in a first phase, the input rotation speed is set to a theoretical value, wherein the theoretical rotational speed is established on the basis of performance specification by the driver and an operating activity. In the first phase, the difference between the input and output rotational speed of the clutch is reduced to zero following a theoretical value curve.
A process for regulating a clutch is known from DE 39 37 976 A1, which serves for vibration isolation. The slip in the clutch is hereby altered in dependence upon a rotational uniformity ascertained at the transmission output.
From EP 0 214 989 B2 it is also known to use a clutch integrated into the automatic transmission as startup element.
The previously unpublished DE 198 40 573 by the applicant describes a process for controlling and regulating a clutch in a continuously variable transmission for a motor vehicle according to which the clutch is controlled and regulated during two operating conditions by means of a first control circuit. The controlled variable here corresponds to the actual value of a differential rotational speed of the clutch. The first condition corresponds to a startup procedure and the second condition corresponds to driving with a variable gear ratio.
A process for controlling and regulating a clutch with an automatic stepped transmission with tractive force interruption or in an automatic load-switchable stepped transmission is known from the likewise unpublished DE 198 40 572. At the same time, the control or regulation takes place during three driving conditions by means of a first control circuit. The controlled variable corresponds to the actual value of a differential rotational speed of the clutch. The first condition corresponds to a startup process, the second condition corresponds to driving with constant gear ratio and the third condition exists when a load switching or a shift in gear ratio from a first into a second gear ratio step of the automatic transmission is initiated.
Underlying the present invention is the objective, proceeding from the previously described state of the art, of indicating a process for controlling and regulating a clutch in a stepped load-switchable automatic gear shift for a motor vehicle as well as a device for carrying out the process for controlling and regulating and to refine this with respect to the multiple use of a single clutch, especially with respect to improved regulation quality and regulation dynamics in connection with a stepped load-switchable automatic transmission.
This objective is attained in accordance with the invention by the objects of the independent claim. Further advantageous configurations are described in the dependent claims.
The invention advantageously consists in that the first control circuit is used for controlling and regulating the coupling during a first driving condition. The controlled variable corresponds to the actual value of the engine speed n_MOT_IST, which corresponds to the input rotational speed of the clutch. During the second driving condition is used a second control circuit, whose controlled variable is equivalent to the actual value of the differential rotation of a clutch dnK_IST, and finally during the third driving condition, the clutch is impinged by a controlled pressure value dependent upon various influence magnitudes. The three driving conditions here correspond to a startup process below a vehicular limiting speed in tractive operation as a first condition, operating beyond the startup process above a vehicular limiting speed with a positive or negative torque in push-pull operation as a second condition as well as operating below a vehicular limiting speed with a negative torque at the output in push operation during the third condition, wherein the startup process differs from the other driving conditions in that the vehicular limiting speed is smaller than a limiting value, and the vehicle engine can be stalled beneath this limiting speed.
Through the process of the invention, advantageously a better reaction of the transmission control is obtained on load switching, especially when removing the gas in the third condition, since here the pressure value of the clutch is only controlled and not regulated.
Furthermore, the clutch differential rotational speed is not reset to a zero value so that, in this way, advantageously a vibration isolation between the vehicle engine and the transmission is reached.
In an advantageous refinement of the invention, it is proposed that the load switching be decisively determined by a third control circuit, and that the first and third or the second and third control circuit be connected with each other through a decoupling network, wherein the decoupling network in any given case has a first and a second signal path. With a load switching in the sense of a cross-over circuit, an internal control circuit, namely the third control circuit, consequently determines the behavior of the clutches to be switched on or off. Since during load switching, due to the rotatory masses to be delayed or accelerated, it comes to an influencing of the clutch, it is suggested for this case that the first and third or the second and third control circuit be connected to each other via a decoupling network in such a manner that the two regulators, which are in use, are advantageously not mutually influenced in their action.
With a load switching from a first into a second gear ratio step of the automatic transmission during the first operating condition, the first control circuit operates by means of the decoupling network via the first signal path on the third control circuit and the third control circuit operates by means of the decoupling network via the second signal pathway back to the first control circuit.
With a load switching from a first into a second gear ratio step of an automatic transmission during the second operating condition, the second control circuit operates by means of the decoupling network via the first signal pathway on the third control circuit and the third control circuit operates by means of the decoupling network via the second signal path on the second control circuit.
In a refinement of the invention, it is proposed that the pressure level pAK of the clutch in the first and the second condition be computed on the basis of an offset value pAK_OFF and a summation value pSUM. The summation value pSUM is decisively determined from the balance of the control torque MK (ST) of the clutch, the regulated summation torque MK(RE)= of the clutch and the decoupled load switching torque MLS_ENT.
The controlled torque MK(ST) is decisively determined on the basis of the dynamic clutch torque MDYN_MOT and a regulated torque MK(RE).
The regulated summation torque MK(RE)xe2x80x2 of the clutch is determined on the basis of the dynamic engine torque MDYN_MOT and a regulated torque MK(RE).
The regulated torque MK(RE) in the first operating condition is decisively determined on the basis of the theoretical/actual comparison of a magnitude equivalent to a engine speed n_MOT and a performance specification DKI of a driver by means of a regulator.
The gear-dependent theoretical rotational speed dn_SW(i) for a startup gear of the automatic transmission is determined in a second driving condition through a characteristics map KFI(i), i=1, 2. This characteristics map here represents an allocation of performance specifications of the driver (DKI) and output rotational speed nAB of the clutch.
During a load switching of the stepped automatic transmission, a shift from a first characteristics map KFI(i1) into a second characteristics map (KFI(i2) takes place.
The regulated torque in the second operating condition MK(RE) is definitively determined on the basis of the theoretical/actual comparison of the rotational speed differential dnK_SW, dnk_IST of the clutch and a performance specification DKI of a driver by means of a regulator.
Advantageously, the regulator contains a restricted integrator wherewith the integrator is fed as input magnitudes the system deviation on the basis of the theoretical/actual comparison of the rotational speed differential dnK_SW, dnk_IST of the clutch, the set speed of the performance specification DKI, and the ratio of the actual to the theoretical value of the differential rotational speed dnK_IST/dnK_SW of the clutch.
Advantageously, the theoretical value of the differential rotational speed dnK_SW of the clutch results from the addition of the theoretical value offset dnLS_SW and a gear-dependent differential rotational speed dn_SW(i) of the clutch.
Advantageously, during a transition from the first or third driving condition into the second driving condition, the theoretical value of the differential rotational speed dnk_SW is led through a filter, especially a dynamic delaying element, whereby the current actual value of the differential rotational speed is set as the initial value of the delaying element.
In a refinement of the invention, it is suggested that, in the second condition, the theoretical value offset of the differential rotational speed dnLS_SW of the clutch be increased during load switching from a first i1 into a second gear ratio step I2 of the automatic transmission in the load assumption and gradient adjusting phase, and be reduced again when ending the concluding phase.
A switch from a gear-dependent characteristic map KF(i1) to a characteristic map (KF(i2) also takes place here during load switching.
The characteristics maps are here constructed such that with a vehicular speed v smaller than a limiting value GW, an elevated differential rotational speed dn_SW(i) of the clutch results. In this way, an active stalling protection for non-startup gears, thus, for example, the fourth or fifth gear of the automatic transmission, is attained.
Advantageously, an elevated differential rotational speed dn_SW(i) of the clutch is calculated as stalling protection in the second operating condition as well. Here the elevated differential rotational speed dn_SW(i) is set greater than the difference on the basis of the most minimal rotational speed of the internal combustion engine n_MOT_MIN and the output rotational speed of the clutch nAB.
In the third operating condition, the pressure level pAK of the clutch results on the basis of a pressure value, which is dependent upon one or more of the following magnitudes: Butterfly valve setting, brake activation, braking pressure, engine torque, load switching or the like, and wherein the pressure value is a controlled magnitude.
Advantageously, a device for carrying out a process for controlling and regulating a clutch in a stepped load-switchable automatic transmission for a motor vehicle is also being indicated. For this, an electronic control device with a first and a second control circuit is provided, whereby the controlled variable of the first control circuit is equivalent to the engine speed, and the controlled variable of the second control circuit is equivalent to the actual value of a differential rotational speed of the clutch.
Furthermore, a third control circuit is provided, which is connected via a decoupling network to the first and the second control circuit, and whereby the third control circuit definitively determines load switching.
Furthermore, the decoupling network has one first and one second control signal path each between the first and third and between the second and third control circuit.